Previous studies have demonstrated the presence of an extrahypothalamic GnRH, immunologically, biologically and chemically identical to the hypothalamic hormone in a variety of tissues in humans. The evidence for the presence of GnRH and receptor in human endometrium remains scattered as well as its possible dynamic changes throughout the menstrual cycle of fertile women are unknown. Objective: To evaluate the expression of GnRH and its receptor at the level of both mRNA and protein in human endometrium throughout the menstrual cycle of fertile women. Methods: Endometrial tissue samples from 26 fertile premenopausal patients undergoing laparoscopic surgery for benign reasons were obtained and classified according to the time of collection and histological dating. Competitive RT/PCR and semiquantitative immunohistochemical studies were performed to evaluate the mRNA and protein levels respectively during the different phases of the menstrual cycle. Results were analyzed by independent sample T-test. Results: GnRH is expressed throughout the entire menstrual cycle of fertile women at the mRNA and protein level. GnRH receptor mRNA is present in all the samples studied. Competitive PCR documents a dynamic pattern of GnRH mRNA throughout the menstrual cycle with a statically significant (P < 0.05) rise in the lutheal phase as compared to the follicular phase. The immunohistochemical study has show the presence of GnRH in both the endometrial stroma and epithelium throughout the entire menstrual cycle, however the immunostaining was intense during the entire luteal phase in the stroma as well as in the luminal epithelium during the mid luteal phase. Conclusions: Our results demonstrate the presence of GnRH and its receptor in the endometrium of fertile women at mRNA and protein levels during the entire menstrual cycle with a dynamic pattern showing an increase in the lutheal phase compared to the follicular phase.